FWIW, StreetComplete considers opening hours that can be unambiguously parsed but are invalid according to the spec as immediately due for re-survey, i.e. an opening hours quest is created. (And completely invalid opening hours strings anyway.)
When the user then acknowledges that the displayed times are still correct or edits the opening hours, a valid opening_hours in canonical form is saved.
In general, the app asks if any opening hours are still correct once every year. This only works if either the shop hasn’t been edited for at least one year or a check_date:opening_hours with a date that is more than one year old has been set. I.e. the app won’t ask if the opening hours are still correct for most shops whose opening hours syntax you corrected just now for another year now.